Binder resin and synergist composition including a parting agent and process of making lignocellulosic articles

ABSTRACT

A method for preparing compression molded or pressed lignocellulosic articles is disclosed. The method involves forming a binder resin by combining a polyisocyanate component with a parting agent and preferably a synergist. The parting agent is the reaction product of an isocyanate compound and an isocyanate-reactive compound of the general structure R—(ao) n —Y where: R is a hydrophobic group containing alkyl, alkaryl, polyaryl, or siloxane moieties; (ao) is an alkylene oxide or mixture of alkylene oxides; n is from 1 to 25; and Y represents a monofunctional isocyanate-reactive group. A resinated lignocellulosic mixture is formed by combining the binder resin with lignocellulosic particles. Then a compression molded or pressed lignocellulosic article is formed by compressing the resinated lignocellulosic mixture at an elevated temperature and under pressure. It is particularly preferred that the binder resin further include a synergist of either a C 1-4  N-alkylpyrrolidone, gamma-butyrolactone, or a mixtures of them. The most preferred synergist is N-methyl-2-pyrrolidine.

FIELD OF THE INVENTION

[0001] The invention relates to a process for making compression moldedor pressed lignocellulosic articles by adding a binder resin including aparting agent to lignocellulosic particles and thereafter eitherpressing the mixture between plates or compressing it in a mold at anelevated temperature and pressure and, more specifically, a method formaking compression molded or pressed boards using a binder resincomprising a polyisocyanate component, a parting agent and a synergistcomponent.

BACKGROUND OF THE INVENTION

[0002] It is known to make compression molded or pressed lignocellulosicarticles, such as particle board, Medium Density Fiberboard (MDF)agrifiber board (such as straw board or bagasse, etc.), and orientedstrand board, by coating or contacting lignocellulosic particles with abinder resin to form a lignocellulosic mixture, optionally adding otheradditives including parting agents or wood preservatives and compressingthe mixture at elevated temperatures and pressures for a time sufficientto make commercially useful articles, such as, boards.

[0003] The lignocellulosic particles can be in the form of chips,shavings, strands, wafers, fibers, sawdust, bagasse, straw and woodwool. When the particles are relatively larger in size, the boardsproduced by the process are known in the art under the general term ofengineered wood. These engineered woods include panels, laminated strandlumber, oriented strand board, parallel strand lumber, and laminatedveneer lumber. When the lignocellulosic particles are relativelysmaller, the boards are known in the art as particleboard and fiberboard.

[0004] The engineered wood products were developed because of theincreasing scarcity of suitably sized tree trunks for cutting lumber.Such products can have advantageous physical properties such as strengthand stability. Another advantage of the engineered wood and particleboards is that they can be made from the waste material generated byprocessing other wood and lignocellulosic materials. This leads toefficiencies and energy savings from the recycling process, and saveslandfill space.

[0005] The binder used to make the lignocellulosic articles is typicallya resinous material. One common class of binders are resins produced bypolymerizing formaldehyde with other resin forming monomers, includingurea, melamine, and phenol. In certain applications, articles made withsuch binders are deficient in some property such as water resistance.

[0006] Another class of binders are the organic diisocyanate orpolyisocyanate binders. One of the advantages of this class is itssuperior resistance to water. A disadvantage of the typical isocyanatebinders is their relatively high viscosity, which can lead to problemswith delivery of the binder onto the particles. This high viscosity alsorequires that excess binder be used to fully coat the particles.

[0007] In the past various solvents have been added to thepolyisocyanate binder compositions with the aim of achieving a lowerviscosity and better handling properties. After application, the solventgenerally evaporates during the molding process, leaving the boundparticles behind. One major disadvantage of prior art solvents is thatthey cause a reduction in the physical properties of the formed boardincluding a reduction in the internal bond strength of the formed board.

[0008] For example, it is known to use dialkyl carbonate solvents inisocyanate binder compositions for coating lignocellulosic particlesprior to compression at high temperature and pressure to makemanufactured lignocellulosic articles. The isocyanate bindercompositions with dialkyl carbonates are reported to have a lowerviscosity than the free isocyanates, leading to advantages in their usein the process.

[0009] In the above examples, however, the use of the solvent systemdoes not lower the amount of isocyanate binder composition required forachieving best results, also the solvent systems generally lower thephysical properties of the produced board.

[0010] It is therefore an object of the present invention to provide asolvent system for an isocyanate binder composition, which will not onlyact as a diluent but also increase the efficiency of the binder resinwhen it is used to coat or contact lignocellulosic particles prior topressing at high temperature and pressure.

[0011] Another common disadvantage of the use of isocyanate binderresins is their poor release properties from molds or press parts usedto form lignocellulosic articles, which can lead to problems duringmanufacture of the lignocellulosic articles when the mold or press partsstick to the articles.

[0012] To overcome the sticking, it is desirable to use a parting agenteither internally as a component of the binder resin, or externally byapplying it to the press parts between runs. External parting or releaseagents are less preferred because their use involves the extra step ofapplying the agents to the press parts.

[0013] It is therefore, an object of the present invention to provide aparting agent for an isocyanate binder resin, which will not onlydisplay the desired parting properties but will also be compatible withan isocyanate binder resin.

SUMMARY OF THE INVENTION

[0014] In one embodiment, the present invention is a method forpreparing a compression molded or pressed lignocellulosic articlecomprising the steps of: forming a binder resin by combining from about75 to 99.5 weight percent based on the total weight of the binder resinof a polyisocyanate component with from about 25 to 0.5 weight percentbased on the total weight of the binder resin of a parting agent,comprising the reaction product of an isocyanate compound and anisocyanate-reactive compound of the general structure

R—(ao)_(n)—Y

[0015] wherein R is a hydrophobic group containing alkyl, alkaryl,polyaryl, or siloxane moieties, wherein the alkyl moieties comprisestraight chain or branched hydrocarbons with 6 or more carbon atoms, thealkaryl moieties comprise monoalkyl, dialkyl, or trialkyl substitutedaromatic hydrocarbons with 9 or more carbon atoms, the polyaryl moietiescomprise a polyphenyl structure that is either alkyl substituted orunsubstituted, and the siloxane moieties comprise a trisiloxane orhigher polysiloxane; (ao) is an alkylene oxide or mixture of alkyleneoxides selected from the group consisting of ethylene oxide, propyleneoxide, butylene oxide, and mixtures thereof; n is from 1 to 25; and Yrepresents a monofunctional isocyanate-reactive group. In a second stepa resinated lignocellulosic mixture is formed by combining from about 1to 10 weight percent based on the total weight of the lignocellulosicmixture of the binder resin with from about 99 to 90 weight percentbased on the total weight of the lignocellulosic mixture oflignocellulosic particles, the lignocellulosic particles having amoisture content of from 2 to 15 weight percent. Then a compressionmolded or pressed lignocellulosic article is formed by compressing theresinated lignocellulosic mixture at an elevated temperature and underpressure. It is particularly preferred that the binder resin furtherinclude a synergist selected from the group consisting of C₁₋₄N-alkylpyrrolidones, gamma-butyrolactone, and mixtures thereof. The mostpreferred synergist is N-methyl-2-pyrrolidine.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0016] In accordance with the present invention there is disclosed aprocess that utilizes an isocyanate binder resin for the preparation oflignocellulosic articles. The binder resin comprises an organic di- orpolyisocyanate, a parting agent and optionally, a synergist selectedfrom the group consisting of C₁-C₄ N-alkyl pyrrolidones,gamma-butyrolactone, and mixtures thereof. Throughout the presentspecification and claims the terms compression molded or pressed areintended to refer to the same process whereby the article is formed byeither compression molding the article in a mold or by using compressionas between a pair of plates from a press. In both procedures pressureand heat are used to form the article and to set the binder.

[0017] In the present specification and claims the term polyisocyanatecomponent is intended to include a single polyisocyanate and mixtures ofpolyisocyanates. The isocyanate compounds useful in the presentinvention comprise the organic di- and polyisocyanates, modifiedisocyanates, isocyanate-terminated prepolymers, and mixtures of theseisocyanates, all described below. Organic polyisocyanates which may beused include aliphatic, alicyclic and aromatic polyisocyanatescharacterized by containing two or more isocyanate groups. Suchpolyisocyanates include the diisocyanates and higher functionalityisocyanates, particularly the aromatic polyisocyanates. Mixtures ofpolyisocyanates which may be used include, crude mixtures of di- andhigher functionality polyisocyanates produced by phosgenation ofaniline-formaldehyde condensates or as prepared by the thermaldecomposition of the corresponding carbarnates dissolved in a suitablesolvent, as described in U.S. Pat. Nos. 3,962,302 and 3,919,279, thedisclosures of which are incorporated herein by reference, both known ascrude diphenylmethane diisocyanate (MDI) or polymeric MDI. The organicpolyisocyanate may be isocyanate-terminated prepolymers made by reactingunder standard known conditions, an excess of a polyisocyanate with apolyol which, on a polyisocyanate to polyol basis, may range from about20:1 to 2:1. The polyols include, for example, polyethylene glycol,polypropylene glycol, diethylene glycol monobutyl ether, ethylene glycolmonoethyl ether, triethylene glycol, etc., as well as glycols orpolyglycols partially esterified with carboxylic acids includingpolyester polyols and polyether polyols.

[0018] The organic polyisocyanates or isocyanate-terminated prepolymermay also be used in the form of an aqueous emulsion by mixing suchmaterials with water in the presence of an emulsifying agent. Theisocyanate compound may also be modified isocyanates, such as,carbodiimides, allophanates, isocyanurates, and biurets.

[0019] Also illustrative of the di- or polyisocyanates which may beemployed are, for example: toluene-2,4- and 2,6-diisocyanates ormixtures thereof; diphenylmethane-4,4′-diisocyanate anddiphenylmethane-2,4′-diisocyanate or mixtures of same, the mixturespreferably containing about 10 parts by weight 2,4′- or higher, makingthem liquid at room temperature; polymethylene polyphenyl isocyanates;naphthalene-1,5-diisocyanate; 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate; triphenyl-methane triisocyanate;hexamethylene diisocyanate; 3,3′-ditolylene-4,4-diisocyanate; butylene1,4-diisocyanate; octylene-1,8-diisocyanate; 4-chloro-1,3-phenylenediisocyanate; 1,4-, 1,3-, and 1,2-cyclohexylene diisocyanates; and, ingeneral, the polyisocyanates disclosed in U.S. Pat. No. 3,577,358, thedisclosure of which is incorporated herein by reference. Preferredpolyisocyanates include 2,4′-MDI, 4,4′-MDI, 2,2′-MDI, polymeric MDI, andmixtures thereof.

[0020] Typical of the preferred isocyanates are those sold under thetrademark Lupranate® by BASF Corporation. For example Lupranate® MI, anisomeric blend of 2,4′ and 4,4′ MDI isomers or Lupranate® M20 SB, apolymeric MDI.

[0021] The synergist component useful in the resin binders of thepresent invention includes lower N-alkylpyrrolidones. In general, theC1-C4 N-alkylpyrrolidones are useful in the present invention, with thepreferred N-alkylpyrrolidone being N-Methyl-2-pyrrolidone. Other usefulsynergists include gamma-butyrolactone. Mixtures of the above synergistscan also be used to form the synergist component.

[0022] The resin binder of the present invention can also contain othersolvents, so long as the physical properties of the resultinglignocellulosic article are not adversely affected. For example, it ispreferred to avoid xylene as a component of the resin binder, becausethe use of xylene leads to a lower value of internal bond in theresulting lignocellulosic article.

[0023] The resin binder can also contain other conventional additives,such as parting agents or wood preservatives. Suitable parting agentsare described fully below. When the resin binder includes such optionaladditives, efficiency is gained because the resin binder and any othernecessary ingredients can be coated onto the lignocellulosic particlesin a single step.

[0024] The synergist component can be combined with the polyisocyanatecomponent in an amount from 0.5 to 25 weight percent based on the totalweight of the binder resin. More preferably, the binder resin includesfrom 0.5 to 15 weight percent, and most preferably 0.5 to 10 weightpercent synergist based on the total weight of the binder resin. Thebinder resin preferably comprises from about 75 to 99.5 weight percentpolyisocyanate component, and more preferably from about 85 to 99 weightpercent polyisocyanate component based on the total weight.

[0025] The lignocellulosic particles can be derived from a variety ofsources. They can come from wood and from other products such asbagasse, straw, flax residue, nut shells, cereal grain hulls, andmixtures thereof. Non-lignocellulosic materials in flake, fibrous orother particulate form, such as glass fiber, mica, asbestos, rubber,plastics and the like, can be mixed with the lignocellulosic material.The lignocellulosic particles can come from the process of comminutingsmall logs, industrial wood residue, branches, or rough pulpwood intoparticles in the form of sawdust, chips, flakes, wafer, strands, mediumdensity fibers (MDF), and the like. They can be prepared from variousspecies of hardwoods and softwoods. It is important that thelignocellulosic particles have a moisture content of from 2 to 15 weightpercent. In a further preferred embodiment the water content is from 3to 12 weight percent, and most preferably from 4 to 10 weight percent.The water is utilized during the curing of the binder resin. If thewater content is outside of this range the binder resin is not asefficient at forming the molded article.

[0026] The lignocellulosic particles can be produced by variousconventional techniques. For example, pulpwood grade logs can beconverted into flakes in one operation with a conventional roundwoodflaker. Alternatively, logs and logging residue can be cut intofingerlings on the order of about 0.5 to 3.5 inches long with aconventional apparatus, and the fingerlings flaked in a conventionalring type flaker. The logs are preferably debarked before flaking.

[0027] The dimensions of the particles are not particularly critical.Flakes commonly have an average length of about 2 to 6 inches, andaverage width of about 0.25 to 3 inches, and an average thickness ofabout 0.005 to about 0.05 inches. Strands which are about 4 cm wide and12 cm long can be used to make laminated strand lumber, while strandsabout 0.3 cm wide and 25 cm long can be used to make parallel strandlumber.

[0028] The wood particles can be further milled prior to use in theprocess of the invention, if such is desired to produce a size moresuitable for producing the desired article. For example, hammer, wingbeater, and toothed disk mills may be used.

[0029] The lignocellulosic particles are resinated using the binderresin described above. The binder resin and the lignocellulosicparticles are mixed or milled together during the formation of aresinated lignocellulosic mixture. Generally, the binder resin can besprayed onto the particles while they are being agitated in suitableequipment. To maximize coverage of the particles, the binder resin ispreferably applied by spraying droplets of the binder resin onto theparticles as they are being tumbled in a rotary blender or similarapparatus. For example, the particles can be resinated in a rotary drumblender equipped with at least one spinning disk atomizer. One advantageof the present invention is that the binder resin forms smaller dropletsthan typical polyisocyanate binder resins leading to better coverage ofthe particles.

[0030] For testing on a lab scale, a simpler apparatus can suffice toresinate the particles. For example, a 5 gallon can is provided withbaffles around the interior sides, and a lid with a hole large enough toreceive the nozzle of a spray gun or other liquid delivery system, suchas a pump sprayer. It is preferred that the binder resin be delivered asa spray. The particles to be resinated are placed in a small rotaryblender. The blender is rotated to tumble the particles inside againstthe baffles, while the desired amount of binder resin is delivered witha spray device. After the desired amount of binder resin is delivered,the particles can be tumbled for a further time to effect the desiredmixing of the particles with the binder resin.

[0031] The amount of binder resin to be mixed with the lignocellulosicparticles in the resinating step is dependant upon several variablesincluding, the binder resin used, the size, moisture content and type ofparticles used, the intended use of the product, and the desiredproperties of the product. Generally, the amount of binder resin tomixed with the particles is from 1 to 10 weight percent based on thetotal weight of the resinated lignocellulosic mixture. In a preferredembodiment the amount of binder resin is from 1 to 4 weight percentbased on the total weight of the resinated lignocellulosic mixture.

[0032] The mixture produced during the resinating step is referred to inthe art as a furnish. The resulting furnish, i.e., the mixture offlakes, binder resin, parting agent, and optionally, wax, woodpreservatives and/or other additives, is formed into a single ormulti-layered mat that is compressed into a particle board or flakeboardpanel or another composite article of the desired shape and dimensions.The mat can be formed in any suitable manner. For example, the furnishcan be deposited on a plate-like carriage carried on an endless belt orconveyor from one or more hoppers spaced above the belt. When amulti-layer mat is formed, a plurality of hoppers are used with eachhaving a dispensing or forming head extending across the width of thecarriage for successively depositing a separate layer of the furnish asthe carriage is moved between the forming heads. The mat thickness willvary depending upon such factors as the size and shape of the woodflakes, the particular technique used in forming the mat, the desiredthickness and density of the final product and the pressure used duringthe press cycle. The mat thickness usually is about 5 to 20 times thefinal thickness of the article. For example, for flakeboard or particleboard panels of ½ inch thickness and a final density of about 35lbs/ft³, the mat usually will be about 3 to 6 inches thick. After matformation, a paper overlay, like that used in furniture panels or forexterior siding, can be applied to the mat prior to pressing.

[0033] Press temperatures, pressures and times vary widely dependingupon the shape, thickness and the desired density of the compositearticle, the size and type of wood flakes, the moisture content of thewood flakes, and the specific binder used. The press temperature can befrom about 1000 to 300° C. In order to minimize generation of internalsteam and the reduction of the moisture content of the final productbelow a desired level, e.g., about 8 to about 12%, the press temperaturepreferably is less than about 250° C. and most preferably from about180° to about 240° C. The pressure utilized is generally from about 300to about 800 pounds per square inch. Preferably the press time is from120 to 350 seconds. The press time utilized should be of sufficientduration to at least substantially cure the binder resin and to providea composite article of the desired shape, dimension and strength. Forthe manufacture of flakeboard or particle board panels, the press timedepends primarily upon the panel thickness of the article produced. Thepressure applied by the press is correlated with the press temperatureso that the moisture content of the final product is from about 8 to12%. For example, the press time is generally from about 200 to about300 seconds for a pressed article with a ½ inch thickness.

[0034] Oriented Strand Board Manufacture

[0035] Oriented strand board (OSB) can be made by the process of theinvention from a plurality of discrete generally oriented strands orstrips of wood hot pressed together using a binder resin, such as thebinder resin of the present invention described above. The pieces orstrips of wood are, for example, plywood or veneer strips having a widthof about ¼ inch to ⅜ inch, a length of about 2½ inches to about 3 inchesand a thickness of about 20 mils. The strips of wood are generallyoriented so that the fiber direction is approximately the same. Theresinated, oriented strips are disposed into a press or mold so that thestrips are in contact with other strips both vertically and horizontallyso that when pressed under heat and pressure the strips are compressedtightly against other contacting strips to adhere the strips togetherand to mold a sheet of material having desired dimensions. The strandsor strips of wood material are not perfectly aligned in one fiberdirection (approximately ±20° from a single direction) so that somestrips overlap other adjacent strips for stronger adhesion.

[0036] Oriented strand boards are prepared in a pilot plant according tothe process described above. The strands are obtained from a commercialmill and are predominantly poplar. The strands are resinated in a rotarydrum blender equipped with at least one single spinning disk atomizerusing 2.5 weight percent of the binder resin. Such blenders are known inthe art and are available from suppliers such as Coil Manufacturing,they typically include up to six spinning disk atomizers in eachblender. The press cycle is a total of 4 minutes with a presstemperature of about 205° C. A commercially available external releaseagent, a water based organosiloxane emulsion, is coated on the innermold surfaces. The target size of the boards is 2 feet by 2 feet by{fraction (7/16)} inch, with a density of 39 pounds per cubic foot. Atotal of 24 boards are produced. Twelve of the boards are produced by aconventional process, wherein the resination step is accomplished with abinder resin containing only Lupranate® M20 SB (“M20SB”), a polymericMDI material sold by BASF Corporation. The other twelve are produced bythe process of the current invention, wherein the binder resin contains10 weight percent of N-methyl-2-pyrrolidone (“NMP”) and 90 weightpercent of Lupranate® M20 SB. Eight boards, four from each group oftwelve, were randomly chosen for evaluation of average density andinternal bond strength (IB). The results are given in Table 1.

[0037] In Table 1, the IB is given in units of pounds per square inch,or psi. Internal bond strength, is a commonly measured parameter oflignocellulosic articles manufactured by pressing binder coated woodparticles at high temperature and pressure. It measures theeffectiveness of the binder resin. The higher the IB, the stronger isthe article or board made by the process. For Table 1, IB is measuredaccording to ASTM D-1037. TABLE 1 ORIENTED STRAND BOARDS Density, IBExample Binder Resin composition (lbs/ft³⁾ (psi) 1 100% M20SB 38.7 51.82 100% M20SB 39 56.1 3 100% M20SB 38.1 39.0 4 100% M20SB 40.4 45.5 5 90% M20SB + 10% NMP 40.4 63.9 6  90% M20SB + 10% NMP 39.9 55.3 7  90%M20SB + 10% NMP 40.2 52.1 8  90% M20SB + 10% NMP 39 51.6 Average 100%M20SB 38.8 48.1 Average  90% M20SB + 10% NMP 39.9 55.7

[0038] It is seen from Table 1 that boards made using a binder resinwhere 10% of the polymeric MDI is replaced by NMP are at least asstrong, based on measurement of IB, as are boards made using a binderwhich is 100% MDI. In fact, the results suggest that the NMP enhancesthe strength of the formed internal bonds (average of 55.7 with 10% NMPversus 48.1 with no NMP). While not wishing to be bound by anyparticular theory it is believed that the NMP dissolves the lignin inthe lignocellulosic material thereby enhancing the penetration of thebinder resin and its adhesion to the lignocellulosic particles.

[0039] In another experiment boards are prepared as described aboveusing several levels of NMP and the viscosity of the binder resin ismeasured in addition to IB. The results are presented below in Table 2.TABLE 2 ORIENTED STRAND BOARDS Binder resin Viscosity at 25° Density, IBExample composition (centipoise) (lbs/ft³⁾ (psi) 1 100% M20SB 209 38.954 2  95% M20SB + 130 * *  5% NMP 3  90% M20SB + 83 39.9 56  10% NMP

[0040] The results demonstrate the significant reduction of viscosityprovided by the present binder resin without a reduction in the internalbond strength that would be expected based on typical solvents.

[0041] The present invention further teaches a parting agent, whichcomprises the reaction production of an isocyanate compound and anisocyanate-reactive compound for use with the binder resin of thepresent invention.

[0042] The isocyanate compounds useful in the parting agent comprise theorganic di- and polyisocyanates, modified isocyanates,isocyanate-terminated prepolymers, and mixtures of these isocyanates,all described below.

[0043] The isocyanate compound which may be used includes aliphatic,alicyclic and aromatic polyisocyanates characterized by containing twoor more isocyanate groups. Such polyisocyanates include thediisocyanates and higher functionality isocyanates, particularly thearomatic polyisocyanates. Mixtures of polyisocyanates may also be usedand include, crude mixtures of di- and higher functionalitypolyisocyanates produced by phosgenation of aniline-formaldehydecondensates or as prepared by the thermal decomposition of thecorresponding carbamates dissolved in a suitable solvent, as describedin U.S. Pat. Nos. 3,962,302 and 3,919,279, both known as crudediphenylmethane diisocyanate (MDI) or polymeric MDI.

[0044] The organic polyisocyanate may be an isocyanate-terminatedprepolymer prepared by reacting, an excess of a polyisocyanate with apolyol which, on a polyisocyanate to polyol basis, may range from about20:1 to 2:1. The polyols include, for example, polyethylene glycol,polypropylene glycol, diethylene glycol monobutyl ether, ethylene glycolmonoethyl ether, triethylene glycol, etc., as well as glycols orpolyglycols partially esterified with carboxylic acids including allpolyester polyols, and all polyether polyalkylene polyols. Such polyolsare well known in the art and will not be further described.

[0045] The isocyanate compound may also be modified isocyanates, suchas, carbodiimides, allophanates, isocyanurates, and biurets.

[0046] Also illustrative of the di- or polyisocyanates which may beemployed are, for example: toluene-2,4- and 2,6-diisocyanates ormixtures thereof; diphenylmethane-4,4′-diisocyanate anddiphenylmethane-2,4′-diisocyanate or mixtures of same, the mixturespreferably containing about 10 parts by weight 2,4′-MDI or higher,making them liquid at room temperature; polymethylene polyphenylisocyanates; naphthalene-1,5-diisocyanate; 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate; triphenyl-methane triisocyanate;hexamethylene diisocyanate; 3,3′-ditolylene-4,4-diisocyanate; butylene1,4-diisocyanate; octylene-1,8-diisocyanate; 4-chloro-1,3-phenylenediisocyanate; 1,4-, 1,3-, and 1,2-cyclohexylene diisocyanates and; ingeneral, the polyisocyanates disclosed in U.S. Pat. No. 3,577,358, thedisclosure of which is incorporated herein by reference. Preferredpolyisocyanates include 2,4′-MDI, 4,4′-MDI, 2,2′-MDI, polymeric MDI, andmixtures thereof.

[0047] Typical of the suitable polyisocyanates are those sold under thetrademark Lupranate® by BASF Corporation. For example, Lupranate® MI, anisomeric blend of 2,4′ and 4, 4′ MDI isomers, or Lupranate® M20 SB, apolymeric MDI.

[0048] The isocyanate-reactive compound can be represented by thegeneral structure R(ao)_(n)Y. Here Y represents a monofunctional groupwhich is reactive with isocyanates. Examples include monoalkylamino andhydroxyl, with hydroxyl being preferred. In the structure above, (ao)represents an alkylene oxide or mixture of alkylene oxides such asethylene oxide, propylene oxide, butylene oxide, and mixtures thereof; nrefers to the number of alkylene oxide units in the isocyanate-reactivecompound. It is conventional to use the symbol (ao)_(n) to represent apolyoxyalkylene chain comprising, on average, n repeating units ofalkylene oxide. In the invention, a preferred alkylene oxide is ethyleneoxide. The variable n can be integer or non-integer and is in generalfrom about 1 to about 25, more preferably from about 2 to about 25, andmost preferably from about 3 to about 10.

[0049] In the isocyanate reactive compound R—(ao)_(n)—Y, R represents ahydrophobic group. The hydrophobic group is based either on hydrocarbonsor on silicon-containing compounds.

[0050] Preferred hydrocarbon hydrophobic groups include in general thosecontaining alkyl, alkaryl or polyaryl moieties. Alkyl moieties useful inthe invention include those with about 6 or more carbon atoms. Examplesare hexyl, octyl, nonyl, decyl, dodecyl, and hexadecyl. Useful alkarylmoieties include the aryl hydrocarbons such as alkaryl, dialkaryl, andtrialkaryl hydrocarbons, wherein the alkyl groups contain at least about3 carbon atoms. Together with the 6 carbon atoms of the aromatic ring,there are thus 9 or more carbon atoms in the preferred alkaryl,dialkaryl, and trialkaryl hydrocarbons. Examples include octylphenyl,hexylphenyl, nonylphenyl, dioctylphenyl, dinonylphenyl, trioctylphenyl,trinonylphenyl, and trialkarylphenyl groups. Particularly preferred arethe alkaryl and dialkaryl groups such as nonylphenyl and dinonylphenyl.The polyaryl compounds have the general structure of a polyphenylstructure that is either alkyl substituted or unsubstituted. Thus in thepresent specification and claims the term polyaryl means a polyphenylstructure that is either alkyl substituted or unsubstituted.

[0051] Examples of isocyanate-reactive compounds useful in the inventionthus include alcohol alkoxylates, alkylphenol alkoxylates, anddialkylphenol alkoxylates. Examples of alcohol alkoxylates include thefatty alcohol ethoxylates which are made by adding 2-20 units ofethylene oxide onto a C₆-C₁₈ straight chain or branched alcohol. Theseare available commercially, for example, under the Iconol® trademarkfrom BASF Corporation. Examples of useful alkylphenol alkoxylatesinclude those made from alkylphenols having three or more carbons in thealkyl chain attached to the phenol ring. Commonly available commercialalkylphenol alkoxylates include octylphenol ethoxylates and nonylphenolethoxylates which are made by adding about 2 to about 20 units ofethylene oxide to octylphenol or nonylphenol. They are sold, forexample, under the tradenames Iconol® OP and Iconol® NP by BASFCorporation. Similarly, dialkylphenol ethoxylates are useful in theinvention. Examples are alkoxylates of those dialkylphenols ortrialkylphenols having three or more carbon atoms in each alkyl group.Especially preferred are the ethoxylates of dialkyl- or trialkylphenolsmade by adding about 2 to about 20 units of ethylene oxide to, forexample, a dialkylphenol such as dioctylphenol or dinonylphenol.Dinonylphenol ethoxylates are available commercially from BASFCorporation under the Macol® DNP tradename.

[0052] Where R represents silicon-containing compounds, the preferredhydrophobic group comprises siloxane groups. Generally preferred are thedimethylsiloxanes including trisiloxanes and higher polysiloxanes. Apreferred isocyanate-reactive compound comprises a silicone compound ofgeneral structure

[0053] wherein Q is a bridging group of one or more atoms, m is 0-10, pis 0-10, R1 and R2 are independently alkyl or alkaryl groups containing1 to 18 carbon atoms, (ao) is an alkylene oxide or mixture of alkyleneoxides selected from the group consisting of ethylene oxide, propyleneoxide, butylene oxide, and mixtures thereof, Y represents amonofunctional isocyanate reactive group, and n is from about 2 to about20.

[0054] Preferably R1 and R2 are alkyl groups containing 1-10 carbonatoms. More preferably, R1 and R2 contain 1-4 carbon atoms. Mostpreferably, R1 and R2 are methyl. R1 and R2 may be different, but it ispreferred that they be the same. It is particularly preferred that R11and R2 are both methyl. The subscripts m and p are preferably from zeroto 2; in a particularly preferred embodiment, m and p are both zero.When m and p are both zero, the compound is a trisiloxane. Where the sumof m and p is greater than zero, the compound is a higher polysiloxane.A particularly preferred trisiloxane containing isocyanate-reactivecompound is commercially available from BASF Corporation as Masil®SF-19.

[0055] Such silicon containing isocyanate-reactive compounds can besynthesized, for example, by the reaction of R1,R2-terminatedhydro-functional polysiloxane of general structure

[0056] where R1, R2, m, and p have the same meaning as above, with anadduct of an unsaturated alcohol and alkylene oxides. The adduct can beprepared by reacting the unsaturated alcohol with ethylene oxide or amixture of alkylene oxides in the presence of base catalysis. Thus, whenthe unsaturated alcohol is allyl alcohol, the adduct will have thegeneral structure CH₂═CH—CH₂—(ao)_(n)—OH, where ao represents theethylene oxide units or mixture of alkylene oxide units, and nrepresents the degree of alkoxylation. When the olefin of the allylalcohol adduct reacts with the Si—H bond of the hydro-functionalpolysiloxane, a bridging group Q is formed consisting of the threecarbon atoms of the ally alcohol portion of the adduct.

[0057] When Y of the isocyanate reactive compound comprises a hydroxylgroup the reaction product will contain urethane linkages formed fromthe reaction of the isocyanate groups of the isocyanate compound withthe hydroxyl group of the isocyanate-reactive compound. Similarly when Ycomprises an alkylamino or other nitrogen containing isocyanate-reactivegroup, the resulting reaction product will contain urea linkages, basedon the reaction of the isocyanate groups with the nitrogen of theisocyanate-reactive compound.

[0058] The parting agents of the present invention may also containchemical modifications of the urethane or urea linkage, such asallophanates, carbodiimides, biurets, and uretonimines. In generalallophanate linkages are formed from the reaction of an isocyanate groupwith a urethane group. Generally the allophanate reaction is carried outwith special allophanate catalysts and at a temperature relativelyhigher than that at which the urethane is formed from the reaction ofisocyanate and hydroxyl.

[0059] The parting agent of the present invention can be prepared orsynthesized by a number of routes. In general, an isocyanate compoundand an isocyanate-reactive compound of general structure R(ao)_(n)Y arecharged together into a reaction vessel. Thereafter, they are allowed toreact for a time sufficient to react out substantially all of the Ygroups on the isocyanate-reactive compound and all of the isocyanategroups on the isocyanate compound. Preferably there is less than 2.5%residual free NCO after the formation of the parting agent, morepreferably less than 1.0% and most preferably less than or equal to 0.2%free NCO after the reaction is complete. It is desirable to have thesevery low levels of free NCO when using the parting agent in a binderresin for wood particles, as described below. These low levels of freeNCO prevent migration of the parting agent into the wood particles.Excess isocyanate reactive compound can be tolerated because it does notpresent any such problem.

[0060] Where the isocyanate compound and isocyanate-reactive compoundare charged in stoichiometrically equivalent amounts, there is produceda parting agent which contains either urethane linkages or urealinkages, depending on whether Y in the isocyanate-reactive compound isa hydroxyl group or an alkylamino group, respectively. For this reactionthe reaction temperature is set at a temperature of about 40° C. toabout 100° C. Higher or lower temperatures can also be used, but thegiven range provides good results. The reaction can be monitored byfollowing the isocyanate number of the reaction product over time. Thereaction can be stopped when the desired isocyanate number is reached.The reaction will proceed without catalysts. However urethane catalystsmay be added to the reaction mixture. Examples of suitable catalystsinclude potassium octoate, zinc acetylacetonate, potassium hydroxide,and organo tin compounds.

[0061] To form parting agents which contain allophanate linkages,further steps are required. For example, after charging the isocyanatecompound and the isocyanate-reactive compound in stoichiometricallyequivalent amounts and reacting at a temperature of from about 40° C. toabout 100° C. until the desired intermediate isocyanate number isreached, a second charge of the isocyanate compound can be added to thereaction vessel.

[0062] Further reaction is then carried out at a second temperaturehigher than about 40° C. to about 100° C. for a period of timesufficient to react substantially all of the isocyanate added in thesecond charge. Along with the second charge of isocyanate compound, itis generally necessary to also add a catalyst which aids in theformation of the allophanate groups. Such allophanate catalysts areknown in the art and include zinc acetylacetonate, titaniumtetrabutoxide, and ferric chloride. The allophanate reaction ispreferably carried out at a temperature of about 100° C. to about 150°C.

[0063] An alternative method for producing parting agents containingallophanate groups is as follows. First an isocyanate compound and anisocyanate-reactive compound are charged to a reaction vessel in anamount such that the molar ratio of the isocyanate compound toR(ao)_(n)Y is greater then 1:1, that is, such that there is a molarequivalent excess of the isocyanate compound in the reaction vessel. Themixture thus charged is then reacted at a temperature of from about 40°C. to about 100° C. until substantially all of the R(ao)_(n)Y hasreacted. The reaction can be monitored by following the free isocyanatenumber during the reaction. When the desired intermediate % free NCO isreached, the mixture is then reacted at a second temperature higher thanabout 40° C. to about 100° C. The reaction proceeds until substantiallyall of the isocyanate compound has reacted and the isocyanate content ofthe reaction product is equal to or less than the desired level.

[0064] Although if the reaction is carried out at high temperatures fora sufficiently long time, an allophanate catalyst is not absolutelyrequired, it is in general preferred in the last step to also addconventional allophanate forming catalysts such as those describedabove. The allophanate catalysts may be charged to the vessel prior tothe reaction at the first temperature of from about 40° C. to about 100°C. Alternatively, the allophanate catalysts may be charged afterreacting at the first temperature but prior to the reaction at thesecond higher temperature. In general, the allophanate catalyst and thetemperature of reaction are chosen such that during the reaction of theisocyanate compound and isocyanate-reactive compound in the first step,the temperature is lower than that required for efficient allophanateformation. In the reaction at the second temperature the temperature ishigh enough to efficiently convert the remaining isocyanate groups toallophanate.

[0065] Allophanates can be formed when an amount of isocyanate compoundin stoichiometric excess to that of the isocyanate-reactive compound ischarged to the reaction vessel. As discussed above, the charge of excessisocyanate compound can be accomplished in the first step along with thecharge of isocyanate-reactive compound, where the conditions ofcatalysis and temperature are such that the excess isocyanate will notreact further with the urethane or urea linkage being formed in thereaction of the isocyanate compound and the isocyanate-reactivecompound. Alternatively, the excess isocyanate can be introducedfollowing the reaction of stoichiometric amounts of isocyanate-reactivecompound and isocyanate compound.

[0066] In either case, in general, any amount of excess isocyanate canbe added to the reaction mixture. However, it is preferred in making theparting agent of the present invention to use an excess of isocyanatecompound on the order of about 1 to 10 equivalent percent. That is,there should preferably be about a 1 to 10 percent excess of isocyanategroups over isocyanate-reactive groups. It can thus be seen that whenparting agents of the present invention are made which containallophanate linkages, the compositions will also in general contain ureaor urethane linkages.

[0067] The parting agent and the organic di- or polyisocyanate whichcomprises the binder resin should be chosen such that they arecompatible. That is, the two components should be readily soluble ineach other, so that a single phase composition can be obtained. To thisend, it is preferred that the organic di- or polyisocyanate and theisocyanate compound on which the parting agent is based should have asimilar structure. Therefore, a preferred binder resin is one where theorganic di- or polyisocyanate comprises an aromatic di- orpolyisocyanate and wherein the isocyanate compound on which the partingagent is based is also aromatic.

[0068] Preferred organic di- or polyisocyanate include methylenediphenyldiisocyanate isomers such as 2,4′-MDI, 4,4′-MDI, 2,2′-MDI. A suitableisocyanate compound is Lupranate® MI, which is a mixture of 2,4′ and4,4′-MDI isomers, available from BASF Corporation. Another preferredorganic di- or polyisocyanate is polymeric MDI. Mixtures of the abovepreferred di- or polyisocyanates may also be used. A particularlypreferred polyisocyanate comprises polymeric MDI. A useful commerciallyavailable polymeric MDI material is Lupranate® M20S isocyanate sold byBASF Corporation.

PARTING AGENT EXAMPLES

[0069] Example 1 below describes the synthesis of a parting agentwherein the isocyanate compound is a mixture of diphenylmethanediisocyanate isomers, R comprises dialkaryl, Y is hydroxyl, and n isabout 10. Example 2 describes the synthesis of a parting agent whereinthe isocyanate compound is a mixture of diphenylmethane diisocyanateisomers, R comprises trisiloxane, and Y is hydroxyl. Example 3demonstrates formation of a parting agent wherein the hydrophobic groupis an alkaryl. Example 4 is similar to Example 3 with the addition of acatalyst.

[0070] Lupranate® MI isocyanate is a mixture of diphenylmethylenediisocyanates sold by BASF Corporation. Macol® DNP-10 is an average 10mole ethoxylate of dinonylphenol, and Iconol® NP-6 is an average 6 moleethoxylate of nonylphenol; they are commercially available from BASFCorporation.

Example 1 Synthesis of an Internal Parting Agent Where the HydrophobicGroup is Dialkaryl

[0071] Macol® DNP-10 surfactant (428.4 g) is placed in a one liter twoneck flask and heated to 45° C. With continuous agitation, Lupranate® MIisocyanate (71.6 g) is added dropwise over a period of an hour. Thetemperature is increased to 80° C. and the reaction is continued for 20to 24 hours. Titration of remaining free NCO groups shows a % free NCOof about 0.5%. The temperature is maintained for an additional one hour,the reaction mixture is cooled to room temperature and allowed to standovernight. Titration of free NCO after the overnight period shows thereaction is complete—that is, the measured free NCO is 0.1%, which iswithin the error of the method.

Example 2 Synthesis of an Internal Parting Agent Where the HydrophobicGroup is Silicon

[0072] Masil® SF-19 surfactant (423 g) is placed in a one liter threeneck flask and heated to 80° C. with continuous agitation provided by anoverhead stirrer. Lupranate® MI isocyanate (77 g) is added dropwise overa period of about 30 minutes. The temperature is increased to 90° C. andthe reaction is continued for 20-24 hours, after which time the % freeNCO is determined by titration and found to be ca. 0.5%. The reaction iscontinued for an additional 2 hours at 90° C., the reaction mixturecooled to room temperature and allowed to stand overnight. Titration offree NCO shows the reaction is complete.

Example 3 Synthesis of an Internal Parting Agent Where the HydrophobicGroup is Alkaryl

[0073] Iconol® NP-6 (393.5 g) is placed in a one liter two neck flaskand heated to 45° C. With continuous agitation, Lupranate® MI (106.5 g)is added dropwise over a period of an hour. The temperature is increasedto 80° C. and the reaction is continued for 20 to 24 hours. Titration ofremaining free NCO groups shows a % free NCO of about 0.5%. Thetemperature is maintained for an additional one hour, the reactionmixture is cooled to room temperature and allowed to stand overnight.Titration of NCO the following morning shows the free NCO is 0.1%, whichis within the error of the method, thus the reaction is complete.

Example 4 Synthesis of an Internal Parting Agent Where the HydrophobicGroup is Alkaryl

[0074] Lupranate® MI (106.5 g) is placed in a one liter two neck flaskand heated to 45° C. With continuous agitation, Iconol® NP-6 (393.5 g)and 20 ppm of the urethane catalyst DABCO T-12 is added dropwise over aperiod of an hour. The temperature is increased to 80° C. and thereaction is continued for 9 hours. Titration of remaining free NCOgroups shows a % free NCO of about 0.5%. The temperature is maintainedfor an additional one hour, the reaction mixture is cooled to roomtemperature and allowed to stand overnight. Titration of NCO thefollowing morning shows the free NCO is 0.1%, which is within the errorof the method, thus the reaction is complete.

[0075] Procedure For Evaluation of Parting Agent

[0076] The following procedure was used to test the parting agents ofthe present invention prepared as in Examples 1-3. Results of theexperiments are given in Table 3 below.

[0077] 1. The stainless steel caul plates are preconditioned withexternal mold release (i.e. spray a dilute solution of external pressrelease on the caul plate, then wipe off the excess with a paper towel).In the Examples, XCTW-9495, a water based organosiloxane was used as theexternal mold release.

[0078] 2. Raw material (wood fiber, wood flake, wood particle, saw dust,etc.) is blended with a binder resin comprising Lupranate® M20SB, apolymeric MDI sold by BASF Corporation, a parting agent prepared inaccordance with the present invention, and, optionally, a synergistcomponent to form a furnish material. The optional synergists includethe lower N-alkyl pyrrolidones. In general, the C₁-C₄N-alkylpyrrolidones are useful in the present invention, with thepreferred N-alkyl pyrrolidone being N-methyl-2pyrrolidone (NMP). Otheruseful synergists include gamma-butyrolactone. Mixtures of the abovesynergists can also be used to form the synergist component. Thesynergist component can be combined with the polyisocyanate component inan amount of from 0.5 to 25 weight percent based on the total weight ofthe binder resin. More preferably, the binder resin includes from about0.5 to 15 weight percent, and most preferably from about 0.5 to 10weight percent synergist based on the total weight of the binder resin.

[0079] 3. The parting agent and synergist used, are reported in theExamples as weight percent based on the total weight of the binderresin. Between 2.5% and 10% by weight binder resin is used, based on thetotal weight of the raw material lignocellulosic particles. The amountused is reported in the Examples. In the Examples, the lignocellulosicparticles are either sawdust or medium density fibers (MDF).

[0080] 4. A form is used to set the desired size of the board, thefurnish material is layered on the bottom caul plate. In the Examples, a6 inch by 11 inch aluminum form is used. The caul plate is transferredinto the press and covered with another preconditioned caul plate.

[0081] 5. The material is pressed under heat and pressure to produce aboard using typical conditions. Pressing time and temperature vary withboard thickness and the raw material. In the Examples, the boards arepressed for 2 minutes at 350° F. and 520 psi. The press is opened andthe caul plates and board are removed from the press.

[0082] 6. A successful event is one after which the board (a) is readilyremoved from caul plates without difficulty, (b) without leaving residueon the caul plates and (c) without causing surface imperfections on theboard resulting from sticking.

[0083] 7. Repeat steps 2-5 using the same set of caul plates withoutapplying any additional external press release.

[0084] 8. The number of boards successfully made is a measure of theperformance of the parting agent. The higher the number, the better theparting agent. The percent binder resin used is a weight percent basedon the total weight of the raw material. TABLE 3 Wt. % Wt. % partingsynergist Parting agent agent in Wt. % in # of Exam- Raw in binderbinder binder the binder boards ple material resin resin used resinpressed 1 MDF Example 3 10 4 none 5 2 MDF Example 2 10 4 none 9 3 MDFExample 2 10 4 10% NMP 6 4 MDF Example 2  5 4  5% NMP 6 5 SawdustExample 1  5 4 none 7 6 MDF Example 1  5 4  5% NMP 12  7 MDF None  0 4none 1

[0085] Example 7 is a control where no parting agent was used in thebinder resin. With no parting agent, only one board could be pressedbefore re-applying the external release agent. Examples 1-6 show thatthe parting agents of the present invention impart desirable propertiesto the binder resins of the present invention, in that their use in thebinder resins enables 5 to 12 boards to be pressed withoutre-application of the external release agent.

[0086] In addition, all binder resins in Examples 1-6 are of a singlephase and homogenous, indicating that the parting agent is compatiblewith the di- or polyisocyanate, and that the binder resins are stable.

[0087] The foregoing invention has been described in accordance with therelevant legal standards, thus the description is exemplary rather thanlimiting in nature. Variations and modifications to the disclosedembodiment may become apparent to those skilled in the art and do comewithin the scope of the invention. Accordingly, the scope of legalprotection afforded this invention can only be determined by studyingthe following claims.

We claim:
 1. A method for preparing a compression molded or pressedlignocellulosic article comprising the steps of: a) forming a binderresin by combining from about 75 to 99.5 weight percent based on thetotal weight of the binder resin of a polyisocyanate component with fromabout 25 to 0.5 weight percent based on the total weight of the binderresin of a parting agent, the parting agent comprising the reactionproduct of an isocyanate compound and an isocyanate-reactive compound ofthe general structure R—(ao)_(n)—Y wherein R is a hydrophobic groupcontaining alkyl, alkaryl, polyaryl, or siloxane moieties, wherein thealkyl moieties comprise straight chain or branched hydrocarbons with 6or more carbon atoms, the alkaryl moieties comprise monoalkyl, dialkyl,or trialkyl substituted aromatic hydrocarbons with 9 or more carbonatoms, the polyaryl moieties comprise a polyphenyl structure that iseither alkyl substituted or unsubstituted, and the siloxane moietiescomprise a trisiloxane or higher polysiloxane; (ao) is an alkylene oxideor mixture of alkylene oxides selected from the group consisting ofethylene oxide, propylene oxide, butylene oxide, and mixtures thereof; nis from 1 to 25; and Y represents a monofunctional isocyanate-reactivegroup; b) forming a resinated lignocellulosic mixture by combining fromabout 1 to 10 weight percent based on the total weight of thelignocellulosic mixture of the binder resin with from about 99 to 90weight percent based on the total weight of the lignocellulosic mixtureof lignocellulosic particles, the lignocellulosic particles having amoisture content of from 2 to 15 weight percent; and c) forming acompression molded or pressed lignocellulosic article by compressing theresinated lignocellulosic mixture at an elevated temperature and underpressure.
 2. The method according to claim 1, comprising forming theparting agent with an aromatic isocyanate compound.
 3. The methodaccording to claim 1, comprising forming the parting agent with anisocyanate-reactive compound wherein R comprises a polyaryl group. 4.The method according to claim 3, comprising forming the parting agentwith an isocyanate-reactive compound wherein n is from 1 to
 10. 5. Themethod according to claim 1, comprising forming the binder resin and theparting agent with one or more isocyanates selected from the groupconsisting of 2,4′-MDI, 4,4′-MDI, 2,2′-MDI, polymeric MDI, and mixturesthereof.
 6. The method according to claim 1, wherein step a) comprisescombining from about 90 to about 99.5 percent by weight of saidpolyisocyanate component with from about 0.5 to about 10 percent byweight of said parting agent.
 7. The method according to claim 1,wherein step a) further comprises adding from 0.5 to 15 weight percentbased on the total weight of a synergist selected from the groupconsisting of C₁₋₄ N-alkylpyrrolidones, gamma-butyrolactone, andmixtures thereof to the binder resin.
 8. The method according to claim7, comprising adding N-methyl-2-pyrrolidone as the synergist.
 9. Themethod according to claim 1, wherein the temperature is elevated to from100 to 300° C.
 10. The method according to claim 9, wherein thetemperature is elevated to from 180 to 240° C.
 11. The method accordingto claim 1, comprising setting the pressure at from 300 to 800 poundsper square inch.
 12. The method according to claim 1, wherein step c)further comprises compressing the resinated lignocellulosic mixture forfrom 200 to 300 seconds.
 13. A method according to claim 1 wherein stepc) comprises forming a compression molded or pressed lignocellulosicboard.
 14. The method according to claim 1, wherein step b) comprisesforming the resinated lignocellulosic mixture by combining the binderresin with lignocellulosic particles having a moisture content of from 3to 12 weight percent.
 15. The method according to claim 1, wherein stepb) comprises forming the resinated lignocellulosic mixture by combiningthe binder resin with lignocellulosic particles having a moisturecontent of from 4 to 10 weight percent.
 16. The method according toclaim 1, wherein step a) comprises forming the parting agent using anisocyanate-reactive compound where Y is either a hydroxyl group or amonoalkyl group.
 17. The method according to claim 1, wherein theparting agent is formed by combining at least one MDI isomer with anisocyanate-reactive compound where R comprises an alkaryl and Y is ahydroxyl group.
 18. The method according to claim 17, wherein theparting agent is formed with an isocyanate-reactive compound where n isfrom 1 to
 10. 19. The method according to claim 1, wherein the partingagent is formed by combining at least one MDI isomer with an isocyanatereactive compound where R comprises a siloxane moiety and Y is ahydroxyl group.
 20. The method according to claim 19, wherein theparting agent is formed from an isocyanate-reactive compound where n isfrom 1 to
 10. 21. The method according to claim 1, wherein the partingagent is formed by combining at least one MDI isomer with an isocyanatereactive compound where R comprises a polyalkaryl and Y is a hydroxylgroup.
 22. The method according to claim 21, wherein the parting agentis formed from an isocyanate-reactive compound where n is from 1 to 10.